Our first contact took place back in 2018.

Three years later, we received the inquiry described above: in addition to normal milling, the company also wanted to carry out deep drilling up to 1,500 mm on the same machine. Not in field, forest and meadow steel, but in X37CrMoV5-1 stainless steel with a tensile strength of 1,200N/mm² and a hardness of 38HRC! It was immediately clear to us that we couldn’t just do it from the hip!

First test: very promising!

After intensive preliminary discussions, including with the drill manufacturer Botek Präzisionsbohrtechnik, we got down to business. We installed an additional pump on a customer machine – an RT 3000 without a V-axis – which delivers up to 220 liters/min to the drilling point. Because with a drilling diameter of 80 mm, volume is more important than pressure. The “throw line” was connected to the rotary feed-through of the drill, the pilot hole was pre-milled, and off we went. Although “only” with a 650 mm drill bit length due to the machine capacities, this was perfectly adequate for an initial test. And it went extremely well, although the main spindle motor of the test machine was already reaching its performance limit. Conclusion: We can do it, but the desired machine for our deep drilling project requires a few additional options.

What must our dream machine be able to do?

For the really deep drill holes, the test run resulted in additional requirements for the machine: ideally an RT milling machine with a 2000 mm V-axis for the long drills up to 1,800 mm in length; a coolant pump with 250 liters/min; a coolant preparation tank that can also filter the volume; and finally a more powerful main spindle motor. The successful test also convinced our prospective customer of the quality of this concept, and we received the order for the project planning of a corresponding machine. Now, around 18 months later, this very machine is at the customer’s premises. We carried out the final drilling test last week, with highly satisfactory results all round.

Deep drilling on our RT milling machine – the most important data

We have summarized everything you need to know for those interested in technology:

• Drill diameter 80 mm
• Drilling depth 1,500 mm
• Drill length with rotary feed-through for KSS = 1800 mm
• Drill weight approx. 50 kg
• SK 50 holder
• Cutting speed vc = 60
• Feed per tooth = 0.17
• Speed 1/min = 239
• Feed rate vf mm/min = 41

The accuracy achieved was extraordinarily high. The deviation between the entry and exit opening was only 0.08 mm (in X) and 0.4 mm (in Y). This is not easily achieved even with a deep hole drilling machine! According to Botek Präzisionsbohrtechnik, these are also excellent values, especially as the hole is honed afterwards. Once again: We are talking about a milling machine here, not a specialized deep-hole drilling machine with support lynettes.

The attempt was worthwhile.

For everyone. We were curious to see how well our milling machine would perform in unfamiliar territory. The success confirms the concept: deep drilling on a modified MTE is possible, and with top results. However, the focus is on the benefits for our customer, who now also holds the reins when it comes to deep drilling. No more searching for external suppliers who have capacity on a deep hole drilling machine. Full control of all processes, including quality. Better scheduling, lower costs and the added value remains in-house. The project has paid off for everyone!

Profile MTE RT-3000-V (modified)

• X = 3000 mm (lengthwise)
• Y = 1500 mm (transverse)
• Z = 150 0mm (vertical)
• V = 2000mm (transverse 2–> machine stand)
• Turntable 2000 x 2000 mm
• Milling head / heads diagonal design with 0.01°x0.01° and 6000 rpm
• Main spindle with 65kW and 2020Nm
• IKZ 50bar
• Additional connection with quick coupling for drill rotary feed-through with 250 l/min and 12 bar
• Full cabin + extraction and much more.